Monday, May 2, 2011

Leonid Elenin spent a great deal of time searching for a comet and finally found one! That is quite an exciting achievement these days when there are so many eyes looking for comets every night, including robotic eyes! And then even more exiting, to learn that your comet could end up being what's known as a great comet. Great comets are comets that get bright enough that it is plainly visible without even trying to look for it. Comet Hale Bopp was an example of a great comet. But, the excitement faded somewhat as software for predicting the brightness of comets was showing that we might not be able to see it at all with the unaided eye. Well that just changed! The latest calculations are now predicting a brightness of magnitude 4, which means that it will easily be visible to the unaided eye. The scale of brightness used in astronomy is a logarithmic scale from magnitude -27 for the sun to magnitude 32 for an object so dim that not even the Hubble space telescope can image it. So magnitude 4 is great considering that magnitude 6 is just barely bright enough for the unaided eye to see in optimal conditions, a moonless night and in a location far away from city lights for example. And around the 27th of September we would normally not be able to see it because it will be between the earth and the sun, so if you looked in the direction that it is supposed to be in you would also be looking in the direction of the sun and the sun of course is so bright that only the sun can be seen. However, comet Elenin MAY get bright enough at this time that we might be able to see it in the day time in addition to the sun. A conservative estimate is that it may get to magnitude zero at this time. Magnitude zero is very bright for a night time object, but not bright enough to see in the day. Yet if it can get up to several magnitudes brighter at this time, say magnitude -13 for example, the brightness of the moon, you would be able to see it the same way you can see the moon in the day time. Also, depending on how active it gets, it MAY even appear for a few days as though there are two suns in the sky! It would need to approach magnitude -20 or more for this to occur. This is a very exaggerated suggestion, but not completely improbable. This jump in brightness is because all of the reflected sunlight of the tail will be concentrated in one spot as we will be looking down the tail, which will be very nearly pointed in the direction of the earth. To learn more, go to Leonid's article announcing the news on his web site at the following link. Comet Elenin may be brighter than expected